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Re: antrun versus wsl versus cygwin




On Mon, 18 Feb 2019 13:15:02, Franz Fehringer  wrote:

> Am 18.02.2019 um 11:42 schrieb Houder:
[snip]

> > Now show us the output of an antrun script, where the executable
> > is C:\Tools\Cygwin\bin\which and its argument: bash
> 
> <exec executable="C:\Tools\Cygwin\bin\which" failonerror="true">
>   <arg line="bash" />
> </exec>
> <exec executable="bash" failonerror="true">
>   <arg line="-c src/main/resources/build" />
> </exec>
> 
> gives
> 
> [exec] /usr/bin/bash
> [exec] W i n d o w s   S u b s y s t e m   f o r   L i n u x   h a s   n
> o   i n s t a l l e d   d i s t r i b u ti o n s .
> [exec]    D i s t r i b u t i o n s   c a n   b e   i n s t a l l e d
> b y   v i s i t i n g   t h e   M i c r o s o f t   S t o r e :
> [exec]    h t t p s : / / a k a . m s / w s l s t o r e
> 
> It is as if C:\Windows\System32 were hardcoded somewhere
> The ant exec documentation says
> "The <exec> task delegates to Runtime.exec which in turn apparently
> calls ::CreateProcess. It is the latter Win32 function that defines the
> exact semantics of the call. "

Erm, thinking this over ... you may be on the right track ...

After invoking the Windows executable (JVM or whatever) from Cygwin, "bash"
is started using CreateProcess()

    https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-createprocessa

Before it searches PATH, CreateProcess checks "the 32-bit Windows system
directory" for the presence of "bash.exe".

And we know that bash.exe from WSL is present in C:\Windows\System32. That
does explain why the output of bash from WSL is shown, does it not?
(reporting that a distribution is still to be installed).

The above also explains why renaming bash from WSL to "wslbash.exe" forces
CreateProcess() to search for the presence of bash.exe down the PATH.

Henri


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